Why is Firebase NoSQL?

Cloud Firestore is a NoSQL , document-oriented database. Unlike a SQL database, there are no tables or rows.

Firebase applied like NoSQL DB It includes a flexible rules to define how the data should be structured to provide security and flexibility . Firebase is a Database stored as JSON objects, which is easier to use than some SQL databases for the way to handle the data like a tree.16 Kas 2016

The Firebase Realtime Database is a cloud-hosted NoSQL database that lets you store and sync data between your users in realtime. NEW: Cloud Firestore enables you to store, sync and query app data at global scale.